A31F-07
Demonstration of HNO3 Eddy Flux Measurements at the Boulder Atmospheric Observatory Using Active Passivation

Wednesday, 16 December 2015: 09:30
3004 (Moscone West)
Joseph R Roscioli1, Scott C. Herndon1, Mark S Zahniser1, David D Nelson1, Jake Zaragoza2, Ilana B Pollack3 and Emily V Fischer2, (1)Aerodyne Research Inc., Billerica, MA, United States, (2)Colorado State University, Atmospheric Science, Fort Collins, CO, United States, (3)Colorado State University, Department of Atmospheric Science and Department of Chemistry, Fort Collins, CO, United States
Abstract:
Eddy flux measurements of "sticky" molecules have historically proven
difficult due to strong interactions with instrument surfaces. A novel
approach has been developed to improve these response times, enabling
flux measurements of nitric acid (HNO3) and and ammonia (NH3).
Deliberate addition of the vapor of perfluorinated acids and bases into
a sample stream serves to eject existing surface-bound sample molecules
and passivate instrument surfaces. HNO3 response times for an Aerodyne
quantum cascade laser absorption spectrometer (QCLAS) improve by a
factor of 60-fold when actively passivating. This approach was used
during field measurements of HNO3 fluxes at the Boulder Atmospheric
Observatory, where an actively passivated inertial inlet at 8 m height
yielded HNO3 deposition fluxes of 0.5 - 2 nmol/m2/sec. The dependence
of the deposition flux upon urban vs rural outflow is discussed.
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